added "contentLength()" method to Resource abstraction; URL-based Resource...

added "contentLength()" method to Resource abstraction; URL-based Resource variants introspect "last-modified" and "content-length" response headers (SPR-5465); refined "exists()" check for UrlResource (HEAD request) and ClassPathResource (URL resolution)

org.springframework.core/src/main/java/org/springframework/core/io/AbstractFileResolvingResource.java

 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2010 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,8 +18,10 @@ package org.springframework.core.io;
 
 import java.io.File;
 import java.io.IOException;
+import java.net.HttpURLConnection;
 import java.net.URI;
 import java.net.URL;
+import java.net.URLConnection;
 
 import org.springframework.util.ResourceUtils;
 
@@ -81,6 +83,70 @@ public abstract class AbstractFileResolvingResource extends AbstractResource {
 	}
 
 
+	@Override
+	public boolean exists() {
+		try {
+			URL url = getURL();
+			if (ResourceUtils.isFileURL(url)) {
+				// Proceed with file system resolution...
+				return getFile().exists();
+			}
+			else {
+				// Try a URL connection content-length header...
+				URLConnection con = url.openConnection();
+				con.setUseCaches(false);
+				if (con instanceof HttpURLConnection) {
+					((HttpURLConnection) con).setRequestMethod("HEAD");
+				}
+				boolean doesExist = (con.getContentLength() >= 0);
+				if (!doesExist && con instanceof HttpURLConnection) {
+					((HttpURLConnection) con).disconnect();
+				}
+				return doesExist;
+			}
+		}
+		catch (IOException ex) {
+			return false;
+		}
+	}
+
+	@Override
+	public int contentLength() throws IOException {
+		URL url = getURL();
+		if (ResourceUtils.isFileURL(url)) {
+			// Proceed with file system resolution...
+			return super.contentLength();
+		}
+		else {
+			// Try a URL connection content-length header...
+			URLConnection con = url.openConnection();
+			con.setUseCaches(false);
+			if (con instanceof HttpURLConnection) {
+				((HttpURLConnection) con).setRequestMethod("HEAD");
+			}
+			return con.getContentLength();
+		}
+	}
+
+	@Override
+	public long lastModified() throws IOException {
+		URL url = getURL();
+		if (ResourceUtils.isFileURL(url) || ResourceUtils.isJarURL(url)) {
+			// Proceed with file system resolution...
+			return super.lastModified();
+		}
+		else {
+			// Try a URL connection last-modified header...
+			URLConnection con = url.openConnection();
+			con.setUseCaches(false);
+			if (con instanceof HttpURLConnection) {
+				((HttpURLConnection) con).setRequestMethod("HEAD");
+			}
+			return con.getLastModified();
+		}
+	}
+
+
 	/**
 	 * Inner delegate class, avoiding a hard JBoss VFS API dependency at runtime.
 	 */

org.springframework.core/src/main/java/org/springframework/core/io/AbstractResource.java

 /*
- * Copyright 2002-2008 the original author or authors.
+ * Copyright 2002-2010 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -107,6 +107,15 @@ public abstract class AbstractResource implements Resource {
 		throw new FileNotFoundException(getDescription() + " cannot be resolved to absolute file path");
 	}
 
+	/**
+	 * This implementation checks the timestamp of the underlying File,
+	 * if available.
+	 * @see #getFile()
+	 */
+	public int contentLength() throws IOException {
+		return (int) getFile().length();
+	}
+
 	/**
 	 * This implementation checks the timestamp of the underlying File,
 	 * if available.
@@ -142,10 +151,10 @@ public abstract class AbstractResource implements Resource {
 
 	/**
 	 * This implementation always throws IllegalStateException,
-	 * assuming that the resource does not carry a filename.
+	 * assuming that the resource does not have a filename.
 	 */
 	public String getFilename() throws IllegalStateException {
-		throw new IllegalStateException(getDescription() + " does not carry a filename");
+		throw new IllegalStateException(getDescription() + " does not have a filename");
 	}
 
 

org.springframework.core/src/main/java/org/springframework/core/io/ClassPathResource.java

@@ -124,6 +124,23 @@ public class ClassPathResource extends AbstractFileResolvingResource {
 	}
 
 
+	/**
+	 * This implementation checks for the resolution of a resource URL.
+	 * @see java.lang.ClassLoader#getResource(String)
+	 * @see java.lang.Class#getResource(String)
+	 */
+	@Override
+	public boolean exists() {
+		URL url;
+		if (this.clazz != null) {
+			url = this.clazz.getResource(this.path);
+		}
+		else {
+			url = this.classLoader.getResource(this.path);
+		}
+		return (url != null);
+	}
+
 	/**
 	 * This implementation opens an InputStream for the given class path resource.
 	 * @see java.lang.ClassLoader#getResourceAsStream(String)

org.springframework.core/src/main/java/org/springframework/core/io/Resource.java

 /*
- * Copyright 2002-2008 the original author or authors.
+ * Copyright 2002-2010 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -91,6 +91,13 @@ public interface Resource extends InputStreamSource {
 	 */
 	File getFile() throws IOException;
 
+	/**
+	 * Determine the content length for this resource.
+	 * @throws IOException if the resource cannot be resolved
+	 * (in the file system or as some other known physical resource type)
+	 */
+	int contentLength() throws IOException;
+
 	/**
 	 * Determine the last-modified timestamp for this resource.
 	 * @throws IOException if the resource cannot be resolved

org.springframework.core/src/main/java/org/springframework/util/ResourceUtils.java

 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2010 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -246,6 +246,17 @@ public abstract class ResourceUtils {
 		return new File(resourceUri.getSchemeSpecificPart());
 	}
 
+	/**
+	 * Determine whether the given URL points to a resource in the file system,
+	 * that is, has protocol "file" or "vfs".
+	 * @param url the URL to check
+	 * @return whether the URL has been identified as a file system URL
+	 */
+	public static boolean isFileURL(URL url) {
+		String protocol = url.getProtocol();
+		return (URL_PROTOCOL_FILE.equals(protocol) || protocol.startsWith(URL_PROTOCOL_VFS));
+	}
+
 	/**
 	 * Determine whether the given URL points to a resource in a jar file,
 	 * that is, has protocol "jar", "zip", "wsjar" or "code-source".